British tour operators typically follow official Government advice when assessing security risks. However, the Foreign Office has not yet warned against travel to the monastery – which, built between 548 and 565AD, is one of the oldest Christian monasteries in the world and a draw for pilgrims.

“Excursions to St Catherine’s Monastery have been halted as a precaution,” said a spokesman for Thomas Cook. “Our experienced team on the ground has again assured us that our customers in Sharm el Sheikh and Hurghada [another Red Sea resort, on the Egyptian mainland] are enjoying their holidays.

“We continue to monitor the situation in Egypt and are in regular contact with the Foreign Office. Currently the Foreign Office does not see any risk of travel to the Red Sea resorts and we are happy to report that we continue to operate our flight and holiday programme as normal.”

He added that Thomas Cook was continuing to offer other excursions from Sharm El Sheikh.

Sunday’s roadside bomb struck as the bus approached the town of Taba, on the border with Israel, and is thought to be the work of terrorist insurgents based in the Sinai. It marks a dramatic shift in their current campaign against the Egyptian regime, which to date has targeted the military and police, and comes the just days after Hisham Zaazou, the country’s tourism minister, visited London to reassure prospective holidaymakers about security – urging them to “forget about Cairo” and visit places like Hurghada, Sharm El Sheikh, Luxor and Aswan instead. “They are so far away that if you go there you feel like you are in another country altogether,” he said.

Mr Zaazou said today that he was “very disappointed” by the bombing, and that he hoped it was an isolated incident. The Egyptian Tourist Authority said it was “appalled” by the incident, adding that “we undertake the utmost measures to protect tourists in Egypt and are implementing a plan to increase security measures across all sectors of the travel and tourism industry in Egypt.”

Tour operators will also be hoping the attack does not herald a return to previous terrorist campaigns in the Sinai that targeted tourists. In 2004, 31 people were killed when a bomb, one of three planted at the same time in the peninsula, exploded at the Taba Hilton Hotel, less than a mile from the point of Sunday’s attack.

While attacks have occurred on the Sinai peninsular since then, they have been limited to its northern half, where very few travellers visit. The social unrest that has hindered Egypt since the overthrow of Hosni Mubarak in 2011, and seen annual tourism figures plummet by several million in the space of three years, has also left the popular Red Sea resorts largely unaffected. Should visitors be dettered by Sunday’s attack, it will be yet another a major blow to Egypt’s beleaguered tourism industry.

While nowhere near as popular with Britons as Sharm El Sheikh, on the southern tip of the Sinai, Taba, on the peninsula’s east coast, and the nearby resort of Taba Heights, does attract some Britons. Thomas Cook would not comment on whether the attack had prompted any of its customers to cancel their trips.

A spokesman for Hayes & Jarvis, the luxury tour operator, said it had 31 holidaymakers currently in Sharm El Shiekh, with a further 17 due to arrive this week. He added that non had cancelled, and that excursions to St Catherine’s Monastery would continue. “St Catherine’s Monastery does form part of the excursion programme offered by our ground handler, Travco, and there is a great deal of security in place,” he said. “At present Travco is continuing to offer this excursion, but uptake is minimal. We will continue to monitor the situation as our customers’ welfare is of the utmost importance.

“In terms of confidence in the region, Hayes and Jarvis is still receiving enquiries on a daily basis as there are some great deals in place. Pick up to Egypt has naturally slowed in the past nine months, but as time goes on it seems the stigma British tourists originally attached to Egypt is diminishing.”

Should Britons wish to cancel an upcoming trip to any of the Red Sea resorts, including Taba, they will not be entitled to a refund unless the Foreign Office warns against travel.

While the Foreign Office currently advises against travel to the Sinai, it does not including “[resorts such as] Sharm el Sheikh, Taba, Nuweiba and Dahab; St Catherine’s Monastery; road travel between the Red Sea resorts; road travel from the Red Sea resorts to St Catherine’s Monastery; and transfers between the resorts and the airports of Taba and Sharm el Sheikh.”

Since the attack, South Korea has warned its citizens against all travel to the Sinai Peninsula.